scruple
ˈskruːp(ə)l/
noun
plural noun: scruples
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1.a feeling of doubt or hesitation with regard to the morality or propriety of a course of action.“I had no scruples about eavesdropping”
synon 
yms:
qualms, twinge of conscience, compunction, hesitation, reservations,second thoughts, doubt(s), misgivings, pangs of conscience,uneasiness, reluctance More -
2.historicala unit of weight equal to 20 grains, used by apothecaries.“give, daily, one scruple of sulphate of quinine”
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archaica very small amount of something, especially a quality.“in the choice of a second wife, one scruple of prudence is worth a pound of passion”
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verb
3rd person present: scruples
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1.hesitate or be reluctant to do something that one thinks may be wrong.“she doesn’t scruple to ask her parents for money”
synonyms: hesitate, be reluctant, be loath, have qualms about, have scruples about, have misgivings about, have reservations about, stick at, think twice about, baulk at, demur about/from, mind doing something; More antonyms: jump at the chance
Origin
late Middle English: from French scrupule or Latin scrupulus, from scrupus, literally ‘rough pebble’, (figuratively) ‘anxiety
How my heart sings 